Incandescent electric lamp bulb



Sept. 6, 1932. H. H BLAU INCANDESCENT ELECTRIC LAMP BULB Filed Sept. 13,1930 INVENTOR WITNES S enameled bulbs, the enamel Patented Sept. 6, 1932Wires srArEs PATENT. 'OFFlCE 4 HENRY H. BLAU, OF CHARLEROI, PENNSOHARLEROI, PENN GLASS COMPANY, OF VANIA INCANDESCENT ELECTRIC LAMP BULBApplication filed September 13, 1930. Serial No. 481,618.

The invention relates to incandescent electric lamps having bulbs whichare so mod fied that a substantial portion of the illumination producedby a lamp filament is derived from rays reflected from the modifiedportion of the bulb, which portion, in addition to functioning as areflector, is usually translucent to transmit as difiused light aportion of the filament rays which strike it.

Illuminating experts have long sought for a durable electric lamp bulbto modify light emanating from a lamp filament In such a way as tocombine reduced surface brightness with efiiciency in the transmissionan reflection of visible radiation, the bulb being relatively free fromdepreciation both by discoloration or deterioration of the material bywhich it is modified, and being easy and cheap to manufacture.

Electric lamp bulbs of the type herein contemplated have been made ofclear glass with the bowls of the bulbs provided with enameled portionsfor increasing their reflecting properties and for difl'usingtransmitted light. In these kinds of bulbs it has been difficult, if notimpossible, to obtain efficiency in illumination and a proper balancebetween reflected and transmitted light. Also, their manufacture isattended by special operations, such as enameling,which add to the costof their production, and, in the case of is subject to deterioration.Similarly, some bulbs have had their bowls provided with silver coatingsto render them reflecting, and others have been sand blasted 0r etchedto render them translucent. The silvering of such bulbs is objectionablefor the reasons stated with reference to the enameling and casing ofbulbs, and sand blasted or etched bulbs are ineflicient in their lighttransmitting and reflecting properties. Both sand blasting andenamelling are disadvantageous also because these processes tend toweaken the glass.

The object of this invention is to provide an electric lamp bulb whichefliciently produces combined direct and indirect illumination, whichmay be manufactured at a comparatively low cost, and the illuminatingeifid Specifically,

ciency of which will not permanently deteriorate.

The invention is illustrated in the accompanying drawing, of which Fig.1 is a side view of an electric lamp bulb embodying the invention andshownpositioned in a reflector, a cross section of which is illustrated;and Fig. 2 a similar view of a modified form of lamp bulb positioned inan enclosing globe, a cross section of which is illustrated.

It is known to those skilled in this art that the light-transmittingproperties of certain glasses may be modified by heat treatment. it isknown that certain lasses which are normally clear or semi-di using may,by heating to a suitable temperature or by retarding their rates ofcooling, be rendered difiusing. Glasses of this general type are hereindesignated as being thermally opacifiable.

This invention is predicated upon my discovery that from suitablethermally-opacifiable glass compositions, preferably modifications ofthose heretofore known to me, an electric lamp bulb may be integrallyformed and so thermally opacifiecl locally as to provide it with atranslucent portion, which, with low absorption and with low intrinsicbril liancy,transmits from a filament a suitable amount of diffusedlight, and which portion efficiently reflects a large amount of lightthrough another portion of the bulb which is not thermally opacified.The bulbs thus provided are further characterized by being formed ofuniform homogeneous glass, instead of being weakened or modified as isthe case in enamelling and sand blasting.

In the practice of the invention, a bulb of the desired shape and sizefor its intended use may be blown in the usual or any desired manner.-As is usual, the bulb is preferably formed of substantially uniformthickness through-out. Either asa part of its forming operation, or by asubsequent procedure, the bulb is so treated as to thermally opacify adesired portion of it. When this is done as a part of the formingoperation, provision is made for cooling and subsequent reheating ofthat portion of the bulb which it is desired to thermally opacify, whileeffecting a normal rate of cooling without such reheating of the glassforming the other portion'of the bulb. This may be done by controllingthe relative rates of cooling of the parts of a mold gdjgcent to the twostated portions of the When, as is preferred, the thermal opacificationof a bulb is effected by a procedure subsequent to the blowingoperation, it may e accomplished by heating the portion of the bulbwhich is to be thermally opacified. This may be done by inserting suchportion in a suitable shield or 'casing electrically or otherwise heatedto such a temperature that the portion of the bulb exposed to it isquickly raised to a temperature of from about 950 to 1200 F. The otherportion of the bulb should be shielded from the direct action of theheat in such a way that there is produced an adequately sharp line ofdemarcation between the thermally opacified and un-opacified portions ofthe bulb. The portion of the bulb desired to be thermally opacified maysimilarly be inserted in a suitable opening formed in the wall of agas-fired furnace.

Having reference to the accompanying drawing, an electric lamp is shownin Fig. 1, the lamp including a bulb having its lower portion 2thermally opacified to transmit diffused light through it and to reflectlight through its upper portion 3 for further reflection, by reflector1, for indirect illumination. The upper portion 3 of the bulb, beinguntreated, effectively transmits not only the light reflected upwardlyfrom the treated portion 11, but also the direct upward rays from thefilament 4 of the lamp. The intrinsic brilliancy of the thermallyopacified portion 2 of the bulb being relatively low, the lamp may beviewed without discomfort.

In Fig. 2 an electric lamp having a bulb, such as that just described,is shown positioned within a translucent glass globe 10 such as used forstreet and like lighting, the bulb of the lamp having its outer or upperportion 11 thermally opacified to transmit diffused light through it andto reflect light downwardly through its untreated lower or socket-endportion 12. The major portion of the light rays from the lamp filament13 Which-strikes the treated portion 11 is reflected downwardly throughportion 12 and thence through the lower portion of globe 10 for diffusedlight illumination. Also, direct rays from the filament 13 pass throughthe lower portion of the bulb for similar illumination. In this way,sufficient light is transmitted through portion 11 of the bulb toilluminate the upper portion of the globe, but without a prejudicialwaste of available li ht.

If desired, a bulb may have one of its sides thermally opacified for usein show cases, in store windows, or in association with shallowreflectors, the combined light transmitting rom the the bulbs of asemi-diffusing character to reduce the sharpness of filamentimages andfixture shadows, as is indicated on the untreated portion 12 of the bulbof Fig. 2. When the untreated portion of a bulb 1s to be of cleartransparent glass, as shown in Fig. 1, the relative proportions of thevariout constituents of the glass, and particularly the relativeproportions of its opacifying to its other constituents, are such thatthe opacifying constituent or constitutents do not exert any opacifyingeffect under normal heat treatment of the glass. When the un-' treatedportion of a bulb is to be of semidiffusing character, as shown in Fig.2, the relative proportions of the various constituents of the glass,and particularly the relative proportions of the opacifying to its otherconstituents, are such that the opacifying constituent or constituentsdo not exert their full effect until the bulb is thermally treated in amanner previously explained. With respect to the relative proportions oftheir opacifying to their other constituents, and the relativeproportions of their various constituents to each other, glasses which Ihave used to obtain the results contemplated by this invention differfrom the other the'rmally-opacifiable glasses known to me.

' In the manufacture of bulbs having clear transparent portions for thetransmission of reflected and direct light, glasses resulting from thefollowing batches A and B may be used Ingredients I Batch A Batch B Band1000 1000- Soda ash I 290 292 Aluminum hydrate "I 35 36. Feldspar 680687 N itre 35 36 Barium carbonate Arsenic trioxide 7. 5 7. 7 Sodiumsillcofluoride 82. 5 Litharge 185 locally to form a densehighly-translucent be made from glasses resulting from the glass whichis at the same time highly reflecting. In these glasses opacity does notexist Ingredients Batch D In the glasses resulting from batches C and Dthe constituents are present in such relative proportions to each otherthat, when melted in the above-described manner, there is produced asemi-diflusing glass capable of being rendered highly diifusing andhighly reflecting ,by thermal treatment in a manner previouslydescribed.

. Glasses resulting from the foregoing batches are merely typical, andnot limiting. By the use of these and other thermally-opacifiableglasses, bulbs may be thermally o acified locally to form highlydifiusing an reflecting portions with adequately shar lines ofdemarcation between them and te adjoing glass. Furthermore, the glassesare readily workable, and the thermally opacified portions of bulbs madefrom them are of uniform opacity.

According to the provisions of the patent statutes, I have explained theprinciple and operation of my invention, and have disclosed severalembodiments of it and examples of how it may be practiced. However, Idesire to have it understood that, within the $00 of the appendedclaims, the invention may practiced otherwise than as specificallyillustrated and described.

I claim:

1. An incandescent electric lamp bulb integrally formed throughout of achemicallyhomogeneous thermally-opacifiable glass, one portion of thebulb being thermally opacified to transmit diflused light and to reflectlight through another portion of the bulb.

2. An incandescent electric lamp bulb integrally formed throughout of achemicallyliomogeneous thermally-opacifiable glass, the bowl of the bulbbeing thermally-opacified to transmit diflused light and to reflectlight through the inner portion of the bulb.

3. An incandescent electric lamp bulb integrally formed throughout of achemicallyhomogeneous thermally-opacifiable normally clear glass, oneportion only of the bulb being thermally-opacified to transmit difiusedlight tegrally formed throughout and to neflect light through anotherportion of the bulb.

4. An incandescent electric lamp bulb integrally' formed throughout of achemicallyhomogeneous thermally-opacifiable normally semi-diffusingglass, the bowl of the bulb being thermally-opacified to transmitdiffused light and to reflect light through the inner semi-diffusingglass portion of the bulb adjacent to its socket end.

5. An incandescent electric lamp bulb inof a chemicallyhomogeneousglass, one portion of the bulb 37 being difierentially opacifiedthroughout its entire body to render it translucent to transmit diflusedlight and to reflect light through another portion of the bulb.

In testimony whereof, I si% my name.

HENR H. BLAU.

